Some of the limitations of prior art proximity detectors have been discussed in my U.S. Pat. Nos. 5,287,086 and 5,463,378, each of which being incorporated herein by reference, in which handling unwanted water accumulation in the bilge of a ship is discussed. In the case of marine vessels, pumping of the bilge sometimes results in polluting the environment with oil which is pumped from the bilge along with the water.
In addition to the problems posed in pumping marine bilges in an environmentally proper manner, there are other situations where removal of accumulated water is complicated by factors which significantly reduce the utility of conventional pump controllers.
An example is seen in underground utility vaults containing electrical devices charged with high levels of electrical energy. In some cases, the underground vaults are located near greenbelts, golf courses or in open areas where rainwater or irrigation water can enter the vault. Water accumulated in the vault can cause a potential for shorting electrical devices and in general, can represent a dangerous condition. Thus, it is desirable to prevent vault water from rising above a predetermined level. In this regard, a typical underground vault will have a sump for accumulating water, utilizing conventional methods for removing the water from the sump. Usually, the water is raised to street level where it can be directed into a sewer system. The problem presented by this technique is similar to that of pumping a bilge since oil is sometimes pumped with the water.
Oil is utilized as an electrical insulating agent interposed between high electrical energy switches and metal housing in underground electrical vaults. Over time, as a result of such factors as changing stresses in the earth surrounding the vault, the oil leaks into the vault sump to become layered over the surface of accumulated water.
The relative volumes of oil and water vary from case to case depending on how much oil leakage into the sump is occurring and how much water is invading the vault. Over time, accumulated water and oil results in the sump liquid rising to unacceptable levels.
In conventional systems, when unwanted sump liquids rise to a predetermined level, a float or similar device activates a pump to remove the liquid. In this technique, oil is pumped out of the vault with the water. This presents serious problems in some cases where communities, sensitive to environmental concerns, prohibit the introduction of oil into sewer systems. As a result, the utility company responsible for vault operation is presented with a dilemma. On the one hand, it must remove accumulated water from the electrical vaults while, on the other hand, it is constrained from pumping out vault liquids if oil is one of the liquids.
In an attempt to solve the dilemma, labor intensive techniques are sometimes employed. For example, in some cases where vault liquid accumulation is suspected, a utility company employee is dispatched to enter the vault to insure that, if the pump is activated, no accumulated oil will be pumped out with the water. This inspection process can expose the employee to a dangerous condition requiring entry into a confined space, in the presence of high electrical potential and water. In recognition of the potential danger involved, utility company practices sometimes require a second employee, and in some cases, a third, to be present to monitor the condition of the one in the vault. Such practices are expensive, time consuming and inefficient.
Further complicating the plight of those charged with keeping electrical vaults in a safe and environmentally acceptable condition is that, some community officials, alarmed at the prospect of oil entering the sewer system, have proposed banning the pumping of vault liquids into local sewers.
In cases where bans are implemented, undesirable techniques of vault liquid removal, such as manual bailing or pumping to a transport truck, are sometimes utilized These techniques, while environmentally acceptable, can be expensive, inconvenient and inefficient. Thus, a need exists for a system for removing water from an electrical vault in an environmentally acceptable manner which would reduce or eliminate the need for visual inspection of the vault prior to pumping and would not require transportation of liquids to a remote disposal site.
While conventional devices, disclosed, for example, in U.S. Pat. Nos. 3,553,575; 3,894,240; 3,646,541; 4,053,398; 4,129,501; 4,270,049; 4,523,960 and 5,330,073, none of them represent a solution to the problems set forth above.
In view of the foregoing, it would be advantageous to have a system for removing oil covered water from a vessel, while preventing pumping of the oil. Desirably, such a system would operate with minimal supervision in bilges of marine vessels, underground electrical vaults and other spaces where accumulated water must be removed.